A new evaluation of the Editio Romani, the 16th-century edition of the canon law of the Roman Catholic Church, based on manuscript evidence of the committee's daily activities. This edition of the church's law book was the work of the Correctores Romani commission, especially of Miguel Thom s Taxaquet, and was promulgated by Pope Gregory XIII, the former Ugo Buoncompagni, in 1582 and remained in effect until the 20 th century. This study, the first of its kind, reveals the sophisticated scholarly methodology used by these Catholic Humanists and the censorship that led to the loss of some of their greatest insights. Affiliation and research activities: Mary E. Sommar, Ph.D. teaches European History at Millersville University of Pennsylvania. Her research is concentrated on the history of canon law, especially on the work of Gratian of Bologna and the Corpus Iuris Canonici.